Your statutory right (EU/EEA consumers)
If you're within the EU/EEA and this is your first purchase of a new subscription, you generally have a 14-day right of withdrawal for digital services under EU consumer law, for a full refund, no reason needed. See our Terms of Service for the exact conditions, this right can end earlier than 14 days once you've started actively using the paid features, if you acknowledged that at checkout (this is standard for digital services, since you're getting immediate access rather than waiting for a physical product to ship).
Outside that window
Subscriptions aren't refunded automatically for partial periods. This is because cancelling already keeps you on your paid plan for the rest of the period you paid for, see "How do I cancel my subscription?", so there's no unused time being forfeited.
When we do review a refund case by case
A clear billing error (you were charged twice, or charged the wrong amount) or a service outage that genuinely prevented you from using a plan you paid for. Reach out and describe what happened, these are handled individually rather than by a fixed rule.